Manufacture of artificial silk



Patented Mar. 16, 1937 UNITED STATES PATENT orrics MANUFACTURE ARTIFICIAL SILK No Drawing. Application July 3, 1935,

Serial No. 29,764

3 Claims.

This invention relates to the manufacture of artificial silk and more particularly to the treatment of freshly spun, artificial silk filaments collected in package form.

artificial silk wound in package form, that is, filaments either wound on bobbins, spools and the like or collected in pots by the centrifugal spinning process, the packages were immediately subjected to a washing step to remove the acids,

impurities, et cetera, therefrom. This conventional washing step was conducted by suction, i. e. by drawing water through the packages from the outside to the inside. The packages were washed with water at room temperature.

It was later ascertained that the time consumed to completely remove all of the acids and impurities could be considerably shortened by using water heated to a temperature of from 50 to 55 C. From the standpoint of time consumption the employment of hot water was found to be very beneficial. The hot water also eliminated the black spots on the inside of the packages provided the temperature of the water was above 5 the boiling point of carbon disulphide (46 0.). However, the hot water wash caused an uneven dyeing throughout the bodies of the packages of filaments. By means of a series of experiments the reason for this difference in dyeing was found to reside in the fact that the wet packages, being in compact form, did not allow the water to pass.

through as rapidly as the heat therefrom. Therefore the inner layers of the package prior to washing out the impurities were heated by con- .35 duction to a temperature approximating that of the wash water whereas simultaneously the outer layers were washed acid free. At the elevated temperature the, action of the acid on the filaments was accentuated and therefore the filaments were more completely coagulated on the inner layers of the package with the result that they dyed lighter on the inside than on the outside of the package. Also, the ends of the filament package being thinner were washed acid free more quickly than the middle portion, which resulted in dye differences between the middle and the ends.

The object of this invention is to provide a method of washing packages of artificial silk wherein the above mentioned disadvantages are overcome in a very satisfactory manner, and the packages are washed in a relatively short time while uniform dyeing properties are exhibited therein.

The novel process consists in prewashing the Heretofore during the normal treatment of packages of artificial silk with cool water at approximately 35 C. This prewash is continued until the major portion of the acids is removed. The next step is utilizing wash water at a temperature above 50 C. and preferably at 55 C. to remove the last trace of acids and impurities. It has been found that if during this step an alkali carbonate and/or bicarbonate is added to the wash water, the washing period will be materially lessened. If these said chemicals are employed it is advisable to finally wash the packages of silk with pure water also at a temperature of about 55 C.

The advantages accruing from this improved process are that the cold water removes the major portion of acids whereby when the hot water is subsequently employed the heat will no longer affect the dyeing owing to the absence of acids, and thus the dyeing remains substantially uniform throughout the package. The rate of washing can thereby be hastened during the later stages without harmful effects, and the total time taken is therefore shortened, while uniform dyeing properties of the filament package is retained.

What I claim is:

1. A method of treating artificial silk coagulated in an acid bath which consists in the steps of prewashing freshly spun artificial silk in package form with cool water until the major. portion of the acids is removed therefrom and thereafter subjecting the silk to the washing action of water at a temperature above 50 C. whereby the remaining acids are completely eliminated.

2. A method of treating artificial silk coagulated in an acid bath which consists in the steps of prewashing freshly spun artificial silk in package form with water at approximately 35 C. until the major portion of the acids is removed therefrom, thereafter subjecting the silk to the washing action of water at a temperature of 55 C. whereby the remaining acids are completely eliminated.

3. A method of treating artificial silk coagulated in an acid bath which consists in the steps of prewashing freshly spun artificial silk in package form with water at approximately 35 C. until the major portion of the acids is removed therefrom, thereafter subjecting the silk to the washing action of water containing alkali carbonates and bicarbonates and at a temperature of 55 C. and finally washing with pure water at a temperature of 55 C. whereby the remaining acids and salts are removed.

' HANS ALWIN SCHRENK. 

